The invention is based on a fuel injection pump of the type described hereinafter and finally claimed. In an injection pump known from German Offenlegungsschrift 28 54 422, the full-load injection quantity is limited with the aid of an adjustable stop against which the fuel quantity adjusting member comes to rest at full load. This stop is adjustable in accordance with the pressure of the air delivered to the combustion chambers of the engine, e.g., the charge pressure in the case of supercharged engines. To this end, a pressure box exposed to the charge pressure displaces an adjusting piston provided on its jacket with a contour which is scanned mechanically in order to adjust the stop. In this manner, the fuel injection quantity is adapted to the delivered air quantity. A purely charge-pressure-dependent correction of the injection quantity such as this has the disadvantage that it can follow dynamic load changes only relatively slowly; this is particularly true in the case of devices for compressing the aspirated air which are driven by exhaust gas, because the change in volume of the exhaust gas follows a change in fuel quantity only in a delayed manner. In order to fix the maximum fuel injection quantity at full load, one significant factor in addition to the charge pressure is the rpm. The characteristic fuel supply curves of a supercharger driven by the engine, where the supply pressure is in accordance with the injected fuel quantity, have a successively decreasing slope as the rpm increases. This permissible fuel injection quantity of the supercharged engine also increases with increasing rpm. However, the inclination of the adaptation curve characterizing this permissible fuel quantity has a substantially lower slope than does the slope of the supply curves of the engine/supercharger combination. Thus an error in adjustment which may have arisen at low rpm becomes considerably greater with increasing rpm, which is disadvantageous.
In another known fuel injection pump, disclosed in German Offenlegungsschrift No. 28 47 572, in order to avoid this error, a three-dimensional cam is displaced on the one hand by the rpm-dependent suction-chamber pressure of the injection pump and rotated on the other in accordance with charge pressure. Again, a pressure box exposed to charge pressure is used as the adjusting member, and the three-dimensional curve on the three-dimensional cam is scanned mechanically and transferred to the full-load stop. This has the disadvantage, however, that because of the friction involved in the scanning process, and especially because of the transmission of the governing-spring force onto the scanning pin via the full-load stop, errors of hysteresis occur in adjusting the full-load quantity. Furthermore, the torque which the adjusting box is capable of exerting is quite low, given reasonable dimensions for the adjusting box. Thus, an incorrect adjustment will become magnified with increasing rpm in this form of embodiment as well, because of that portion of the input to the maximum fuel injection quantity which is derived from the charge pressure.